The present invention related to circuit breakers for use in electrical circuits. More particularly, the invention relates to circuit breakers having a mechanical interlock for preventing inadvertent or otherwise unintentional actuation of the circuit breaker.
Safety interlocks are often required on circuit breakers used in medium and high-voltage electrical circuits. Safety interlocks prevent closure of the electrical contacts within the circuit breaker, thereby preventing inadvertent or otherwise unintentional energization of the electrical circuit to which the circuit breaker is coupled.
Magnetic or electrically-actuated circuit breakers commonly use electrical interlocks. Electrical interlocks typically incorporate a switch that selectively interrupts the xe2x80x9cclosexe2x80x9d signal generated by the circuit breaker""s control system, thereby preventing the control system from energizing the actuator that closes the electrical contacts of the circuit breaker.
Electrical interlocks, although proven suitable for their intended purpose in many applications, are generally considered less effective than mechanical interlocks. Mechanical interlocks use some type of mechanical means to block movement of one or more components of the circuit breaker in a manner that prevents the electrical contacts of the circuit breaker from closing. Mechanical interlocks are often preferred or required by regulatory authorities. For example, American National Standards Institute (ANSI) C37.20.2 recommends the use of mechanical interlocks in medium-voltage circuit breakers to prevent the contacts of such breakers from closing unless the breaker is in full contact with a suitable connecting device, or is separated from the connecting device by a safe distance.
Mechanical interlocks, as noted above, rely on some type of physical means to block movement of the electrical contacts therein. Mechanical interlocks, therefore, are usually larger, more complex, and more expensive than an electrical interlock of comparable capability. In addition, the blocking contact between the mechanical interlock and the other components of a circuit breaker can lead to damage or premature wear of the contacting components.
A presently-preferred embodiment of a circuit breaker comprises a frame member, and a contact mechanism fixedly coupled to the frame member and being adapted to be electrically coupled to an electrical circuit. The contact mechanism comprises a first contact member and a second contact member being movable in relation to the first contact member. The circuit breaker also comprises an actuator mechanism fixedly coupled to the frame member. The actuator mechanism comprises an armature mechanically coupled to the second contact member. The armature is adapted to urge the second contact member into electrical contact with the first contact member on a selective basis.
The circuit breaker also comprises a racking mechanism comprising a channel member and a lead screw rotatably coupled to the channel member and the frame member. The frame member is movable between at least two predetermined positions in relation to the channel member in response to rotation of the lead screw. The circuit breaker further comprises a mechanical interlock coupled to the frame member and comprising a blocking pin positioned between the lead screw and the armature when the frame member is located between the at least two predetermined positions. The blocking pin is adapted to inhibit movement of the armature when the blocking pin is positioned between the lead screw and the armature, and thereby prevents the armature from urging the second contact member into electrical contact with the first contact member.
Another presently-preferred embodiment of a circuit breaker comprises a contact mechanism adapted to be electrically coupled to an electrical circuit. The contact mechanism comprises a first contact member and a second contact member being movable in relation to the first contact member. The circuit breaker also comprises an actuator mechanism comprising an armature mechanically coupled to the second contact member. The armature is selectively positionable between a closed position in which the armature urges the second contact member into electrical contact with the first contact member thereby permitting energization of the electrical circuit, and an open position in which the armature urges the second contact member away from the first contact member thereby inhibiting energization of the electrical circuit.
The circuit breaker further comprises a mechanical interlock comprising a blocking pin selectively positionable between a first position proximate the armature and a second position distal the armature. The blocking pin is adapted to interrupt movement of the armature from the open to the closed positions when the blocking pin is in the first position.
Another presently-preferred embodiment of a circuit breaker comprises a frame member movable between a connect position, a test position, and a disconnect position. The circuit breaker also comprises a contact mechanism fixedly coupled to the frame member and adapted to be electrically coupled to an electrical circuit. The contact mechanism comprises a first contact member and a second contact member movable in relation to the first contact member.
The circuit breaker further comprises an actuator mechanism fixedly coupled to the frame member. The actuator mechanism comprises an armature mechanically coupled to the second contact member and adapted to urge the second contact member into electrical contact with the first contact member on a selective basis. The circuit breaker also comprises a racking mechanism comprising a channel member and a lead screw rotatably coupled to the channel member and the frame member and having a first, a second, and a third through hole formed therein. The frame member is movable between the connect, test, and disconnect positions in response to rotation of the lead screw.
The circuit breaker further comprises a mechanical interlock coupled to the frame member. The mechanical interlock comprises a blocking pin and a pivot arm pivotally coupled to the blocking pin and adapted to move the blocking pin between a first position in which the blocking pin is located substantially within one of the first, second, and third through holes, and a second position. The blocking pin substantially aligns with the first, second, and third through holes when the frame member is located respectively in the connect, test, and disconnect positions. The blocking pin is adapted to interfere with movement of the armature when the blocking pin is located in the second position thereby preventing the armature from urging the second contact member into electrical contact with the first contact member.